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The truss-rod is a vital part of the neck - but one that not many knows about. The tension from the strings is more than 800 N and they act like "bow strings" trying to bend the neck like a bow. The truss rod works by adding an additional tension in the opposite direction so the result becomes null (I doubt this is correct English, but I don't find the right words - I hope you understand).

Normally you buy a factory-made truss-rod, but it can be hard to find one, when you're making odd instruments with odd scale lenghts like this one. So I've been used to make my own.

The version I make is an independent package acting as bow and string, glued into the neck.

I begin with this:

A U-shaped aluminum profile, a threaded M6-rod, yet another "IKEA-nut" (a different kind from the one used for the neck) and a common nut. Two small wooden pieces with a hole drilled through them is also included (but not in the picture).

I shape both ends like this:

Then I insert the rod. In one end I attach the normal nut and glues it with epoxy. In the other end I attach the "IKEA"-nut after removing the flange in the grinding stone. I thought that I photo-documented each step, but the pictures are missing. Anyway - when the truss rod is finished I glue it in the slot with LOTS of epoxy and finally I glue a wooden cap at the top. And the result looks like this:

 Now when I tighen the nut, the rod will try to bend the U-profile upwards, hence counteracting the bending from the strings.